Design of a New Hysteretic PWM Controller for All Types of DC-to-DC Converters

A new control method using a hysteretic PWM controller for all types of converters and its proper design method are presented. The triangular voltage obtained from a simple RC network connected between comparator output and converter output is superimposed to the output voltage and as a feedback signal to a hysteretic comparator. Since the hysteretic PWM controller essentially has derivative characteristics and has no error amplifier, the presented method provides no steady-state error voltage on the output and excellent dynamic performances for the load current transient by choosing proper values of time constants in the RC network. Performances of the proposed controller are experimentally verified for the buck, buck-boost and boost converters.